Showing papers on "Myoglobin published in 1971"
316 citations
TL;DR: Evidence is presented that the small amount of impurity in the ferrous sulfmyoglobin preparation is present as oxymyoglobin, and an analysis of optical properties supports the hypothesis of a structure in which the elements of H2S add across a β—β double bond of a pyrrole and thereby disrupt the porphyrin conjugation and form a chlorin type structure.
181 citations
TL;DR: The atomic structure of the monomeric insect haemoglobin is closely similar to the structure of whale myoglobin, although only about 20% of the amino acids are identical in both protein molecules.
Abstract: The atomic structure of the monomeric insect haemoglobin is closely similar to the structure of whale myoglobin, although only about 20% of the amino acids are identical in both protein molecules.
A quantitative comparison of both structures, however, showed that in the vicinity of some amino acid substitutions considerable changes occur. The comparison also revealed unexpected long range structural changes induced by amino acid deletions. In particular a deletion of four amino acids in the A B corner shifts the whole helix B considerably.
The general distribution of amino acids in erythrocruorin is analogous to that which has been found in other haemoglobin molecules. The large proportion of phenylalanines in the hydrophobic core of the molecule is remarkable. Also the haem pocket is lined with seven phenylalanine side chains. Four of these are unknown in vertebrate haemoglobins.
The distal histidine E 7, which is invariant in all known vertebrate haemoglobins, is replaced by a glutamic acid, which has no haem contact, but protrudes into the surrounding solution. This proves that a histidine or another polar residue is not essential for the function of a haemoglobin molecule as a reversible oxygen carrier.
145 citations
TL;DR: In this article, the mean square displacement (x2) from the theoretical lattice point, obtained from X-ray structure data for myoglobin crystals, is compared with the corresponding value, measured by Mossbauer experiments on the iron in myoglobin.
Abstract: The mean square displacement (x2) from the theoretical lattice point, obtained from X-ray structure data for myoglobin crystals, is compared with the corresponding value, (x2)T, measured by Mossbauer experiments on the iron in myoglobin crystals. (x2)T depends only on the vibrations of the lattice. The value (x2), however, which is obtained from X-ray data contains a contribution due to lattice faults in addition to the contribution due to vibrations. (x2) − (x2)T = (x2)S is then the contribution due to lattice faults alone. The experimental values are (x2) = 13.2 × 10−2 A2 and (x2)T = 8.6 × 10−2 A2 giving (x2)S = 4.6 × 10−2 A2. The same comparison was made for K3[Fe(CN)6] and for hemine. Here (x2) was roughly equal to (x2)T. In addition the temperature dependence of (x2)T was measured for myoglobin crystals. A new procedure is described for the substitution of the isotope 57Fe required for Mossbauer measurements for the natural iron in myoglobin.
98 citations
TL;DR: A method of estimating muscle intracellular oxygen tension in vivo, using myoglobin as an oxygen tension indicator, and allows calculation of the mean 02 tension in equilibrium with myoglobin from measurements of mean muscle PCO and carboxymyoglobin percent saturation.
Abstract: COBURN, R. F., AND L. B. MAYERS. Myoglobin 02 tension determined from measurements of carboxymyoglobin in skeletal muscle. Am. J. Physiol. 220(l) : 66-74. 1971.-We have developed a method of estimating muscle intracellular oxygen tension in vivo, using myoglobin as an oxygen tension indicator. The method is based on the competition of oxygen and carbon monoxide for binding sites on myoglobin and allows calculation of the mean 02 tension in equilibrium with myoglobin from measurements of mean muscle PCO and carboxymyoglobin percent saturation. In our experiments the partition of CO between blood and muscle remained constant when the arterial oxygen tension ranged from 40 mm Hg to over 700 mm Hg, but CO shifted out of circulating blood into muscle when the arterial POT fell below 40 mm Hg. The mean myoglobin 02 tension in resting canine hamstring muscle at less than 1 y0 blood carboxyhemoglobin percent saturation and %ormal” arterial Paz (67-l 20 mm Hg) was 4.7 & (SE) 0.3 mm Hg. The mean myoglobin 02 tension decreased approximately 1.5 mm Hg as the arterial Paz was lowered from 490 to 40 mm Hg. When the arterial POT fell below 35-40 mm Hg, the mean myoglobin 02 tension was 0.5-l .5 mm Hg.
86 citations
79 citations
71 citations
TL;DR: Signals assignments were made by comparison of the peptides with each other and with the free amino acids, by the pH dependence of the chemical shifts, and by modification of the degree of proton decoupling in certain cases.
68 citations
TL;DR: The low oxygen affinity of sulfmyoglobin is discussed in terms of structural features of the molecule which lower the electron density at the iron and is an example of electronic control of oxygen affinity in hemoglobin-like compounds.
57 citations
TL;DR: The equation suggested by Wyman (1966) to explain the facilitated diffusion of oxygen in a haemoglobin solution is studied and functional forms for the dependence of the fractional saturation of the protein on the oxygen concentrations at the surfaces of the layer of solution are suggested.
Abstract: The equation suggested by Wyman (1966) to explain the facilitated diffusion of oxygen in a haemoglobin solution is studied. The results for myoglobin are also given. A singular perturbation approach is used which, in this particular situation, reduces the problem from that of solving a nonlinear second-order differential equation to that of solving an algebraic quadratic one. The method also suggests functional forms for the dependence of the fractional saturation of the protein on the oxygen concentrations at the surfaces of the layer of solution through which the oxygen diffuses. The variation in the concentration of free oxygen and the fractional saturation within the layer of solution are given for haemoglobin and myoglobin. The results are consistent with those found experimentally by Wittenberg (1966). A physical implication of the mathematical solution is that the haemoglobin or myoglobin is essentially everywhere in equilibrium with the oxygen in solution. Although this has been conjectured in the past, for example by Wyman (1966), it is motivated here by the mathematics.
TL;DR: The present review calls particular attention to the effects of hemoglobin variants on oxygen transport, which have revealed the functional role of specific portions of the mole cule and have provided further insight into certain types of human disease.
Abstract: The reaction of hemoglobin with oxygen and the mechanisms of adapta tion to hypoxia have intrigued scientists for almost a century. Differences in the oxygen equilibria of myoglobin and hemoglobin have been appreci ated for about seventy years, and various kinetic interpretations of oxygen ation have been presented for nearly half a century. Nevertheless, a deeper understanding of hemoglobin function has only recently emerged, based on the elucidation of the tertiary and quaternary structure of hemoglobin, an appreciation of the allosteric behavior of hemoglobin during oxygenation, and the finding of hemoglobin mutants with altered oxygen dissociation characteristics. These variant structural forms have served as "reagents" in testing hypotheses relating the structure to the function of normal hemoglo bin. They have revealed the functional role of specific portions of the mole cule and have provided further insight into certain types of human disease. The present review calls particular attention to the effects of hemoglobin variants on oxygen transport.
TL;DR: The amino-acid sequence of myoglobin has been fully established in sperm whale, porpoise, harbour seal, horse, and kangaroo and is known partially for the myoglobin of dolphin, Macacus rhesus, humpback whale, Aplysia and man.
Abstract: THE amino-acid sequence of myoglobin has been fully established in sperm whale1, porpoise2, harbour seal2, horse3, and kangaroo4. It is known partially for the myoglobin of dolphin5, Macacus rhesus6, humpback whale7, Aplysia8 and man9.
TL;DR: The peptides were found to have an equal intrinsic helix‐forming tendency which, with only two exceptions, was not raised by the formation of tertiary structure, and these results agree with the demonstrated absence of stable intermediates in protein unfolding equilibria.
Abstract: We have determined the ultraviolet optical rotatory properties of the cyanogen bromide peptides of myoglobin and reduced, S-carboxymethylated α-lactalbumin in both aqueous and aqueous alcohol solutions. Similar measurements were also made on the tryptic digests of apomyoglobin. In aqueous solutions the α-helicity of the various peptides was between 5 and 15%, while in concentrated ethanol solutions the helicity could be increased significantly, but never to more than about 55%. The maximum helicity attained by the various peptides at high ethanol concentrations, as well as the cooperativity of the coil-to-helix transition (reflected in the slope at the steep portion of the helicity-alcohol concentration curves), does not depend on the number of residues in the peptide in the manner expected. We have used a model which treats proline residues as absolute helix breakers, thus introducing the concept of effective chain length. By applying available theories of helix–coil transitions of short-chain polypeptides to this model, one can satisfactorily describe most of the data on the myoglobin peptides. Significantly, it was possible to predict the helicity of acid-denatured apomyoglobin from the behavior of the shorter fragments. By using the model, the peptides were found to have an equal intrinsic helix-forming tendency which, with only two exceptions, was not raised by the formation of tertiary structure. The exceptions were apomyoglobin and peptide 56–131, which show, respectively, a considerable and a very small helicity attributable to tertiary structure formation in water at neutral pH. These results agree with the demonstrated absence of stable intermediates in protein unfolding equilibria. The results offer a further correlation between helical structure in the native molecule and the tendency to helix formation in isolated peptides. The results do not support the hypothesis that small folded regions are responsible for initiating the folding of the molecule, and an alternate description is proposed which envisages approximately half-folded structures at the rate limiting step in the folding reaction. Helix formation in the 33-residue C-terminal peptide of α-lactalbumin was found to be as easy as in the myoglobin peptides. If the proposed structural analogy between lysozyme and α-lactalbumin is correct, then this is a case where helix formation occurs in a peptide which is not helical in the native protein. On the other hand, an α-lactalbumin peptide corresponding to a region which has β-structure in lysozyme did not lend to form α-helices.
TL;DR: This paper has followed the same line of approach to fill the existing gap in the amino acids sequence at position 17-3 1 in the molecule of Black Sea dolphin myoglobin and served as a practical test of the amino acid sequenator built in this laboratory according to Edman’s model.
TL;DR: The relative simplicity of the 13C natural abundance spectra resulting from large chemical shifts, absence of any spin-spin coupling, relatively narrow lines not seriously broadened by dipolar interactions, suggests that better resolution and more detailed information can be obtained from 13C NMR spectra.
TL;DR: Amino acid sequences in myoglobins are more conservative than in the ,B-chains of haemoglobin previously studied but the red kangaroo myoglobin shows more variation in amino acid sequence than has been found in myglobins from other species.
Abstract: Myoglobin isolated from skeletal muscle of M. rufa consists of a single component containing 153 amino acid residues. The complete amino acid sequence has been determined. Oleavage with cyanogen bromide gave four polypeptides which were further fragmented by digestion with trypsin or chymotrypsin. The amino acid sequences of the peptides obtained were determined by the "dansyl"-Edman procedure. The order of the cyanogen bromide fragments was readily deduced from terminal sequences. Digestion of maleylated myoglobin with trypsin and cleavage at histidine residues with N-bromosuccinimide gave some overlapping sequences. Amino acid sequences in myoglobins are more conservative than in the ,B-chains of haemoglobin previously studied (Air and Thompson 1969) but the red kangaroo myoglobin shows more variation in amino acid sequence than has been found in myoglobins from other species.
TL;DR: The oxygen affinities of Buccinum and Busycon myoglobins are greater than the oxygen affinity of their respective haemocyanins and with vertebrate haemoglob Ins.
TL;DR: With the aid of two kinds of spin-labeled protohemins, the nature of the heme-protein interaction of various hemoproteins was investigated and the distance between the iron and the nitroxide radical may be calculated.
Abstract: With the aid of two kinds of spin-labeled protohemins, the nature of the heme-protein interaction of various hemoproteins was investigated Di- and mono-spin-labeled protohemins were prepared from protohemin and 2,2,5,5-tetramethyl-3-aminopyrrolidine-1-oxyl The spin-labeled hemins were recombined with apoproteins of hemoglobin (Hb), myoglobin (Mb), cytochrome c peroxidase (EC 11115) and horseradish peroxidase (EC 11117) Electron paramagnetic resonance spectra of the di- and mono-spin-labeled hemoglobin in 01 M potassium phosphate buffer, pH 70, at 20°C exhibited moderate immobilization of the labels, while that of cytochrome c peroxidase showed stronger immobilization Di-spin-labeled horseradish peroxidase showed an EPR spectrum of a simple broad line with peak-to-peak line width of 35 G This broadening is due to spin-spin interaction between the two labels attached at the 6- and 7-positions of the porphyrin ring Ligand binding to the spin-labeled hemoproteins altered the EPR line shapes and amplitudes The former is attributed to the changes in the mobility of the labels and the latter to the magnetic dipolar interaction between the heme iron and free radical From the strength of this interaction the distance between the iron and the nitroxide radical may be calculated In the hemoproteins examined, the distances are: Hb 125 A, Mb 120 A, cytochrome peroxidase ∼14 A, and horseradish peroxidase 90 A
TL;DR: In a survey of 6000 human muscle samples, four myoglobin variants were discovered by electrophoresis and the second one is of particular interest because it may be the same as Myoglobin Annapolis, described by Boyer, Fainer & Naughton in 1963.
Abstract: Summary.
In a survey of 6000 human muscle samples, four myoglobin variants were discovered by electrophoresis. One has been previously described and this paper gives an account of the second one, which is of particular interest because it may be the same as Myoglobin Annapolis, described by Boyer, Fainer & Naughton in 1963, which at that time could not be completely characterized.
TL;DR: In der glatten Muskulatur des Hühnermuskelmagens konnte ein wasserlösliches Hämoprotein nachgewiesen werden, das sich chromatographisch und spektrophotometrisch wie Myoglobin verhält.
Abstract: In der glatten Muskulatur des Huhnermuskelmagens konnte ein wasserlosliches Hamoprotein nachgewiesen werden, das sich chromatographisch und spektrophotometrisch wie Myoglobin verhalt.
TL;DR: The partial sequence of the first 45 amino acid residues from the NH 2 -terminus of the hemoglobin from Glycera dibranchiata has been determined.
TL;DR: In the absence of variant haemoglobins, myoglobin may be easily distinguished from normal haemoglobin by routine electrophoresis on paper, starch gel, or cellulose acetate at alkaline pH.
Abstract: Victims of severe injuries frequently pass haemoglobin, myoglobin, or both proteins in their urine. If the kidneys of such persons are to be considered as donor material for transplantation, a pathology department may be requested to identify which of these pigments is present. If freshly passed urine is available, haemoglobinuria in the absence of myoglobinuria may be rapidly identified by spectroscopy. However, the rapid degradation of myoglobin to the met-myoglobin form will make spectroscopic recognition of this pigment in the urine unreliable. In the absence of variant haemoglobins, myoglobin may be easily distinguished from normal haemoglobin by routine electrophoresis on paper, starch gel, or cellulose acetate at alkaline pH. The electrophoretic method of choice in the presence of variant haemoglobins utilizes polyacrylamide gel at 12 g/100 ml as a supporting medium. At this concentration, the migration both of haemoglobin and its variants is sufficiently retarded to allow the easy recognition of myoglobin.
TL;DR: The results of an NMR-monitored, acid-base titration of horse CO-Mb (II)* reported here show that at least 6 histidine residues have ‘pp values** between 6.7 and 7.2.
TL;DR: This is the first example of an Arg → Trp substitution, none so far having been found in many families of proteins, which defines the RNA codon for the 138th residue of human myoglobin as CGG and that for another variant 138 Arg → Gln as CAG.
TL;DR: The EPR spectrum of ferric Aplysia myoglobin shows an axial type of high spin signal with g near 6 that changes with pH, and the p K of ionization of the heme-linked water molecule is determined from the pH dependence of this signal.